package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {
    @Resource
    private StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    //普通插入
    public void set(String key, Object value, Long time, TimeUnit unit){
        //value序列化为String类型
        String jsonStr = JSONUtil.toJsonStr(value);
        stringRedisTemplate.opsForValue().set(key,jsonStr,time,unit);
    }

    //逻辑过期
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(redisData));
    }
    //缓存穿透
    public <R,ID> R queryWithPassThrough(String keyPrefix,
                                         ID id, Class<R> type,
                                         Function<ID,R> dbFallback,
                                         Long time, TimeUnit unit
    ){
        String key= keyPrefix + id;
        //1.从Redis中查询
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            //3.不存在，根据id查询数据库
            R r = dbFallback.apply(id);
            //5.数据库不存在，返回错误
            if (r == null) {
                //1.将空值写入Redis
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
                //2.返回错误信息
                return null;
            }
            //6.存在，写入Redis  添加过期时间
            this.set(key,r,time,unit);
        }
        //命中但是为空值
        if(json == ""){
            return null;
        }
        //4.存在，直接返回
        return JSONUtil.toBean(json, type);
    }

    //创建线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    private boolean tryLock(String key){
        Boolean b = stringRedisTemplate.opsForValue().setIfAbsent(key,"1",10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(b);
    }
    //释放锁
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }
    //互斥锁解决缓存击穿
    public <R,ID> R queryWithLogicalExpire(String keyPrefix,
                                           ID id, Class<R> type,
                                           Function<ID,R> dbFallback,
                                           Long time, TimeUnit unit){
        String key= keyPrefix + id;
        //1.从Redis中查询
        String Json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(Json)) {
            //未命中返回空值
            return null;
        }
        //命中，反序列化为对象
        RedisData redisData = JSONUtil.toBean(Json, RedisData.class);
        JSONObject redisDataData = (JSONObject)redisData.getData();
        R rb = JSONUtil.toBean(redisDataData, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //未过期，直接返回商品信息
            return rb;
        }
        //已过期，需要缓存重建
        //获取互斥锁
        String lockKey = LOCK_SHOP_KEY+id;
        //判断是否获取成功
        if (tryLock(lockKey)) {
            //TODO 获取锁成功，开启独立线程
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //查询数据库
                    R r=dbFallback.apply(id);
                    //重建缓存
                    this.setWithLogicalExpire(key,r,time,unit);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //返回过期的商铺信息
        return rb;
    }

}
